As the flowers around us start blooming and the sun starts shining more, it finally begins to feel like spring. Another perk of the new season is that cold and flu season is wrapping up and stuffy noses and irritating coughs are becoming less frequent. Usually when we come down with one of these illnesses, we take Nyquil or another cold-and-flu medicine. One desirable effect of taking this medicine is the suppressed urge to cough. This works because one of the compounds found in cough medicine works on a certain type of receptor in the brainstem called N-Methyl-D-Aspartate (NMDA) receptors. Since these receptors are also present in the insulin-producing cells of the pancreas, scientists have recently uncovered another use for cough medication–the potential treatment of type 2 diabetes.
Type 2 diabetes is an illness that affects nearly 26 million Americans due to the inability of the pancreas to produce insulin or cells having a reduced ability to respond to the insulin hormone, a condition known as insulin resistance. Normally, after a meal is consumed, blood sugar increases. Insulin is then released by the pancreas to transfer the glucose found in the blood to cells in the body for energy usage and storage. Cells respond to the presence of insulin and take in glucose from the blood. However, type 2 diabetes inhibits this process and can cause a multitude of health issues, including cardiovascular disease, blindness, and stroke.
Image Source: Stephen Smith
Current treatments, such as the ones depicted in the image below, are available, but they are often accompanied by adverse side effects, including weight gain, nausea, and diarrhea. A recent study published in Nature Medicine reports that an ingredient found in many over-the-counter cough syrups and medicines improves insulin release by beta cells in humans. The ingredient, dextromethorphan, commonly abbreviated DM, has relatively few minor side effects, especially when compared to medications frequently used to treat diabetes.
Results from experiments with mice were stumbled upon by mistake. Based on previously published studies, the researchers reasoned that inhibiting NMDA receptors could decrease insulin release. To their surprise, they found the opposite reaction. Inhibiting the activity of these receptors in mice and human pancreatic cells led to increased insulin secretion and increased cell survival. Because of these results, researchers used cough medicines, which target NMDA receptors, to determine if the same effect would be seen. They found that when consumed, DM is converted to dextrorphan, and that dextrorphan presence is linked to an increased insulin release from the pancreas.
Dextrorphan suppresses NMDA receptors in the pancreas, increasing glucose-stimulated insulin secretion. Mice that consumed cough medicine had enhanced insulin production, increased numbers of beta cells, and improved control of blood sugar levels. Although the preliminary study results on human and mice pancreatic cells are promising, the human portion of the study only included 20 participants and needs further research, so it is important to note that people with diabetes are not being encouraged to self-medicate with cough syrups. However, the hope is that this study will encourage more clinical trials and longer-term studies in order to find a drug that effectively controls type 2 diabetes.